Why Ana Left Home
During the film, it was mentioned that Ana had not revealed why she had left home. After the interview with Mom and Step-dad, I, and probably others, got a pretty good guess what that reason was. Step-dad announced that his daughter was still a virgin. When asked how he knew this, he replied that he knew from giving her baths. I don't know how many girls that age are still being bathed by a parent, or a step-father, but poking around inside the vagina, examining for an intact hymen seems a little suspicious to me. Not being a parent, I'm not real knowledgeable in this area, but it would seem to me that a parent would have taught the child how to wash themselves by this age, and that an intimate procedure such as this would be performed by a like-sex parent, preferably.
It sounded that it was quite likely that step-dad was doing a little more than bathing here, and running away from home would have been a logical solution for a confused and frightened young girl. Being a very embarassing situation, it's also something that she may not want to reveal to others either, especially if she may think, or have been made to believe, that it is somehow her fault. It's also a possible reason why she came back and snatched her brother too.